Problems existing in the tests of smart substation automation systems are analyzed， and the solution scheme for simulation test of the general IED simulation system based on IEC 61850 standard is put forward. The architecture and functional configuration of simulation system are described. Furthermore， the key technology of the general IED simulation system is implemented， especially the module design of the simulation flow such as: multi-state and multi-timing sequenced signal simulation， closed-loop control simulation and GOOSE simulation. The IED simulation system is developed and successfully applied to integration testing of several smart substation automation systems.